From each sample, approximately 5g of intestinal digesta was weighed and transferred into 10mL of anaerobic FTG broth in a sterile filter-containing Whirl-Pak bag (Nasco, Fort Atkinson, WI). RT-PCR analysis to determine the expression levels of interleukin (IL)-1, interferon- (IFN-), IL-2, IL-13, IL-17, IL-10, and transforming growth factor (TGF)- genes. Levels of antibodies to CP recombinant proteins were also determined in the plasma of experimental chickens. Results indicated that on day 7 post-challenge, IL-1 (proinflammatory cytokine), IL-13 (Th2 cytokine), and IL-17 (Th17 cytokine) were upregulated (P< 0.05) in CP-challenged PCX and PCM treatments, compared to the unchallenged (control) CX and CM treatments. A reverse trend was observed for TGF- (anti-inflammatory cytokine), while no change was observed in IFN- (Th1 cytokine). Levels of plasma antibodies (IgY) to CP recombinant proteins were higher in CP-challenged treatments (PCX and PCM;P< 0.05), compared to their corresponding controls (CX and CM). It was concluded that CP infection induced inflammatory response in the intestine of broiler chickens, and the mechanisms of inflammation are probably mediated via Th2 and Th17 cells. Keywords:Clostridium perfringens, broiler chicken, intestine, Rabbit Polyclonal to NT cytokines, inflammation == INTRODUCTION == Necrotic enteritis toxin B (NetB)-producingClostridium perfringens(CP) type A is the major etiologic agent for necrotic enteritis (NE) in broiler chickens (Cooper et al.,2013; Zhou et al.,2017). CP is a Gram-positive, spore-forming, anaerobic bacterium that is widely distributed in nature, and commonly found in soil, dust, animal production environments such as litter and contaminated feed, and in the gastrointestinal tract of animals and humans as a member of the normal (native) microbiota (Timbermont et al.,2009; Miller et al.,2010). The intestine of healthy birds typically contains approximately 104CFU of CP/g of digesta (McDevitt et al.,2006). However, predisposing factors such as pre-existing damage to the intestinal epithelium by coccidia Bromfenac sodium hydrate (Eimeriaspp.), infectious bursal disease virus, high dietary levels of certain cereals and fish meal, disturbance to the normal intestinal flora, overcrowding, or a variety of management and climatic conditions (McDevitt et al.,2006; Wu et al.,2014) may favor proliferation of CP to reach a critical concentration of about 107to 109CFU/g of digesta (Williams,2005). At this concentration, CP produces toxins that induce mucosal damage in the small intestine and ceca of chickens and turkeys, and results in clinical NE (Van Immerseel et al.,2004,2009). Hostpathogen interaction in NE is complex and involves different components of the host immune system (Oh and Lillehoj,2016). In the chicken intestine, pathogenesis of CP begins with the bacteria penetrating the mucus barrier on the epithelial surface, followed by binding and attachment to epithelial cells. The mechanism by which bacterial pathogens (such as CP) bind to intestinal epithelial cells begins with the recognition and binding of pathogen-associated molecular patterns (PAMPs) by highly conserved pathogen recognition receptors, of which Toll-like receptors (TLRs) are the best characterized (Oh and Lillehoj,2016). It has been established that chickens have at least 10 Bromfenac sodium hydrate TLRs comprising of cell surface-located TLR1a, TLR1b, TLR2a, TLR2b, TLR4, TLR5, TLR15, and intracellular endosome-located TLR3, TLR7, and TLR21 (Chen et al.,2013). In particular, intestinal TLR2 is known to recognize peptidoglycans in Gram-positive bacteria such as CP, and its gene was upregulated in CP-challenged broiler chickens (Du et al.,2016). Interactions between bacterial PAMPs and TLRs trigger a cascade of signaling events that result in the activation of dendritic cells and cellular responses, such as the differentiation of naive T helper (Th) Bromfenac sodium hydrate cells into mature effector Th1, Th2, Th17, and Treg cells (St. Paul et al.,2013; Oh and Lillehoj,2016). These signaling events culminate in the secretion of various cytokines, such as proinflammatory interleukin (IL)-1 by nave Th cells, interferon- (IFN- ) by Th1 cells, IL-13 by Th2 cells, IL-17 by Th17 cells, and transforming growth factor (TGF)- and IL-10 by Treg cells (Cosmi et al.,2014; Narsale et al.,2018). Cytokines are effector molecules that communicate information between cells of the immune system, and the composition of cytokines in the microenvironment of an infection site determines the nature of the immune response affected. Although some studies have studied the response of various cytokines to CP infection or NE disease in broiler chickens (Yitbarek et al.,2012; Alizadeh et al.,2016; Du et al.,2016), robust data are needed especially since the induction of CP infection and NE disease is achieved through various challenge methods (Prescott et al.,2016; Van Waeyenberghe et al.,2016). It has been estimated that annually, NE costs the world poultry industry about $6 billion (US), thereby making it an economically important disease (Wade and Keyburn,2015). Better understanding of.